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| issue date = 04/28/2017
| issue date = 04/28/2017
| title = ASME Section XI Relief Request RR-04-26
| title = ASME Section XI Relief Request RR-04-26
| author name = Sartain M D
| author name = Sartain M
| author affiliation = Dominion, Dominion Nuclear Connecticut, Inc
| author affiliation = Dominion, Dominion Nuclear Connecticut, Inc
| addressee name =  
| addressee name =  
Line 18: Line 18:


=Text=
=Text=
{{#Wiki_filter:Dominion Nuclear Connecticut, Inc. 5000 Dominion Boulevard, G l en All e n , VA 23060 Web Address: www.dom.com U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 April 28 , 2017 DOMINION NUCLEAR CONNECTICUT, INC. MILLSTONE POWER STATION UNIT 2 ASME SECTION XI RELIEF REQUEST RR-04-26 ' 'Dominion Serial No. NRANJDC Docket No. License No. 17-187 RO 50-336 DPR-65 Pursuant to 10 CFR 50.55a(z)(2), Dominion Nuclear Connecticut, Inc. (DNC) requests relief from IWB-3142 of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code for the Millstone Power Station Unit 2 (MPS2) 'B' boric acid pump which has a through-wall leak in the stuffing box cover. The 'B' boric acid pump is one of two redundant pumps used for boron i njection into the reactor coolant system via the suction of the charging pump. Based on recent liquid penetrant examinations , hydrostatic testing, and comparison w i th typical ASME code design rules , DNC has assessed the condition of the stuffing bo x cover as structurally acceptable for continued service. Delivery of a new stuffing box cover is not expected until mid-June 2017. Continued availability of the 'B' boric acid pump is needed to provide defense-in-depth for reactivity control until a permanent code repair of the stuffing box cover is complete. Since ASME Section XI requires the defect be corrected prior to returning the affected component to service , compliance with the requirements of 10 CFR 50.55a would resu l t in a hardsh i p without a compensating increase in the level of quality and safe t y. Attachment 1 to this letter describes the engineering evaluation of the defect , actions that will be implemented by DNC , and the basis for the proposed relief reques t. Attachment 2 provides the non-destructive examination and hydrostatic test reports. DNC requests approval of this relief request by May 5, 2017 to support Cycle 25 operation. This relief request has been approved by the Millstone Facility Safet y Rev i ew Committee. If you have any questions regarding this submittal , please contact Wanda Craft at (804) 273-4687.  
{{#Wiki_filter:~~
-Mark D. Sartain Vice President  
Dominion Nuclear Connecticut, Inc.
-Nuclear Engineering and Fleet Support
5000 Dominion Boulevard, G len All en, VA 23060 Web Address: www.dom.com U.S. Nuclear Regulatory Commission April 28 , 2017
                                                                          ' Dominion Serial No. 17-187 Attention : Document Control Desk                                 NRANJDC    RO Washington, DC 20555                                             Docket No. 50-336 License No. DPR-65 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 2 ASME SECTION XI RELIEF REQUEST RR-04-26 Pursuant to 10 CFR 50.55a(z)(2) , Dominion Nuclear Connecticut, Inc. (DNC) requests relief from IWB-3142 of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code for the Millstone Power Station Unit 2 (MPS2)
'B' boric acid pump which has a through-wall leak in the stuffing box cover. The 'B' boric acid pump is one of two redundant pumps used for boron injection into the reactor coolant system via the suction of the charging pump .
Based on recent liquid penetrant examinations , hydrostatic testing, and comparison with typical ASME code design rules , DNC has assessed the condition of the stuffing box cover as structurally acceptable for continued service. Delivery of a new stuffing box cover is not expected until mid-June 2017 . Continued availability of the 'B' boric acid pump is needed to provide defense-in-depth for reactivity control until a permanent code repair of the stuffing box cover is complete .
Since ASME Section XI requires the defect be corrected prior to returning the affected component to service , compliance with the requirements of 10 CFR 50 .55a would resu lt in a hardship without a compensating increase in the level of quality and safety. to this letter describes the engineering evaluation of the defect, actions that will be implemented by DNC , and the basis for the proposed relief request. provides the non-destructive examination and hydrostatic test reports.
DNC requests approval of this relief request by May 5, 2017 to support Cycle 25 operation . This relief request has been approved by the Millstone Facility Safety Review Committee.
If you have any questions regarding this submittal , please contact Wanda Craft at (804) 273-4687.
Mark D. Sartain Vice President - Nuclear Engineering and Fleet Support
 
Serial No. 17-187 Docket No. 50-336 Page 2 of 2


==Attachment:==
==Attachment:==
: 1. ASME Section XI Relief Request RR-04-26, Boric Acid Pump P-19B Stuffing Box Cover
: 2. Non-destructive Examination (NOE) and Hydrostatic Test Reports Commitments made in this letter: None cc:    U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd Suite 100 King of Prussia, PA 19406-2713 Richard V. Guzman Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 C 2 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station


Serial No. 17-187 Docket No. 50-336 Page 2 of 2 1. ASME Section XI Relief Request RR-04-26, Boric Acid Pump P-19B Stuffing Box Cover 2. Non-destructive Examination (NOE) and Hydrostatic Test Reports Commitments made in this letter: None cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd Suite 100 King of Prussia, PA 19406-2713 Richard V. Guzman Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 C 2 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station ATTACHMENT 1 ASME SECTION XI RELIEF REQUEST RR-04-26 BORIC ACID PUMP P-19B STUFFING BOX COVER MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC. Serial No. 17-187 Docket No. 50-336 Proposed Relief Request RR-04-26 In Accordance with 10 CFR 50.55a(z)(2)  
Serial No. 17-187 Docket No. 50-336 ATTACHMENT 1 ASME SECTION XI RELIEF REQUEST RR-04-26 BORIC ACID PUMP P-19B STUFFING BOX COVER MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.
--Hardship or Unusual Difficulty Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 1 of 1 3 Without Compensating Increase in Level of Quality or Safety--1. ASME Code Components Affected ASME Code Class: Code Class 2  
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 1 of 13 Proposed Relief Request RR-04-26 In Accordance with 10 CFR 50.55a(z)(2)
                              --Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--
: 1. ASME Code Components Affected ASME Code Class:         Code Class 2


==Reference:==
==Reference:==
ASME Section XI , IWC-2500 Examination Category: Table IWC-2500-1 , Category C-H Item Number:            C7.10


ASME Section XI , IWC-2500 Examination Category:
== Description:==
Table IWC-2500-1 , Category C-H Item Number: C7.10
Millstone Power Station Unit 2 (MPS2) 'B' boric acid pump.
Components:              The 'B' boric acid pump stuffing box cover is a casting of type 316 austenitic stainless steel per American Society fo r Testing and Materials (ASTM) A351 CF-8M.
 
===2. Applicable Code Edition and Addenda===
MPS2 is currently in the fourth 10-year inservice inspection (ISi) interval, which started on April 1, 2010 , and ends on March 31 , 2020. The ASME Section XI , 2004 Edition (No Addenda) applies to the ISi program .
 
===3. Applicable Code Requirement===
The ASME Code requirements for this relief request are those associated with Section XI , 2004 Edition , No Addenda, (Reference 8.1) and contained in Article IWB-3142, Acceptance.
 
===4. Background===
The 'B' boric acid pump is one of two redundant pumps used for boron injection into the reactor coolant system. The function of the boric acid pumps is for reactivity control , but the pumps are not credited in the Final Safety Analysis Report, Chapter 14 accident analyses. The design and normal operating parameters for the 'B' boric acid pump are provided below.
Design pressure = 150 psig Design temperature= 250 degrees Fahrenheit Operating discharge pressure = 112 psig Operating suction pressure = 4.5 psig Operating temperature= ambient temperature (110 degrees Fahrenheit)
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 2 of 13 Although MPS2 was designed and licensed to the GDC as issued on July 11 , 1967, DNC has attempted to comply with the intent of the newer General Design criteria to the extent possible, recognizing previous design commitments. MPS2 meets the intent of GDC 26, Reactivity Control System Redundancy and Capability, by employing two independent systems for controlling reactivity changes, including boric acid shim control, of which the boric acid pumps are a part. These systems compensate for long term reactivity changes such as those associated with fuel burnup , variation in the xenon and samarium concentrations, and plant cooldown and heatup. The 'B' boric acid pump provides a redundant means of delivering boric acid to the suction of the charging pumps to control reactivity during normal power operation and for such events as a Technical Specifications required cooldown to cold shutdown.
On February 28 , 2017, during a visual (VT-2) examination of the 'B' boric acid system, dry boric acid residue was identified on the pump stuffing box cover. The source of the boric acid could not be identified. This condition was entered into the corrective action program. During the following sh ift, the boric acid residue was cleaned and the pump was run for two hours in an attempt to determine the leak location and leak rate. No evidence of leakage was observed by the plant equipment operator who was stationed at the pump during the two-hour run.
On March 1, 2017, a follow-up ISi walkdown was performed and dry boric acid residue was found at the same location, but in a smaller quantity. The pump was declared non-functional and corrective action was initiated to identify the source of the leak.
On March 2, 2017, the 'B' boric acid pump was tagged out, but not drained, to support an informational liquid penetrant (LP) examination . The examination found no relevant or recordable indications. Following the LP examination , the 'B' boric acid pump was cleaned and then run for an additional time. After 10 minutes, a small accumulation of boric acid residue appeared as a wet, translucent spot. After 1.5 hours of run time, the wet spot had increased in size to about 1/8 inch in diameter. Although a measurable leak rate could not be determined, growth of the wet spot confirmed the presence of a through -wall leak.            The pump was subsequently isolated on March 9, 2017.
Because of limited access and complex surface geometry, direct volumetric examination of the leakage location from the outside surface of the assembled pump was not possible. However, based on an informational LP examination and visual examination of leakage during an extended pump run , DNC concluded the boundary leakage was likely the result of small voids or porosity present in the original stainless steel casting material.
DNC researched the original purchase order for the pump to identify initial testing associated with the boric acid pump. The pump was constructed in accordance with the draft ASME Code for Pumps and Valves for Nuclear Power, dated November
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 3 of 13 1968, as Class 2, and Combustion Engineering specification 18767-PE-404, Revision 1, dated February 9, 1972. The Combustion Engineering specification refers to the ASME code for testing requirements. Section B of the draft ASME code contains the requirements for Class 2 pumps and valves. Article 23, sub-article 2314 specifies special requirements related to Class 2 components. Normally, this sub-article would require that radiography be performed for a cast product.
However, sub-article 2314 identifies that the special requirements do not apply to materials for pumps and valves with inlet piping connections of four inches and less in nominal pipe size unless otherwise noted in the design specification. The inlet piping to the boric acid pump is less than four inches and the design specification did not invoke a radiography requirement for this pump. Initial testing did include an LP examination and a hydrostatic test and the examination and test had satisfactory results.
Following discovery of the through-wall leak, DNC submitted a purchase order to the pump vendor for a new stuffing box cover. Due to the long lead time to fabricate a replacement stuffing box cover, a code repair of the 'B' boric acid pump was not possible prior to the scheduled shutdown date for 2R24. However, based on engineering assessment of the as-found condition, DNC had high confidence that structural integrity of the stuffing box cover would be maintained for the duration of Cycle 24 operation and execution of the plant shutdown and core offload for 2R24.
Therefore, on March 29 , 2017, DNC requested relief (Reference 9.1) from IWB-3142 of Section XI of the Code to provide continued availability of the 'B' boric acid pump for the remainder of Cycle 24 operation and execution of the plant shutdown and core offload for 2R24. Compliance with the requirements of 10 CFR 50 .55a would have resulted in a hardship without a compensating increase in the level of quality or safety. Verbal approval of the relief request was granted by the NRC the same day (ADAMS Accession No. ML17088A719).
The stuffing box cover on the 'B' boric acid pump has since been removed for furthe r characterization of the through-wall flaw. Based on LP examination and hydrostatic testing , DNC has assessed the stuffing box cover as structurally acceptable for continued service. Details of that evaluation are provided in Section 6 below.
 
===5. Reason for Request===
The 2004 ASME Section XI code was reviewed for acceptance standards associated with the stuffing box cover leak. Table IWC-3410-1 , Acceptance Standards, indicates for pressure retaining components (examination category C-H),
the acceptance standard is IWC-3516. IWC-3516 refers to IWB-3522. IWB-3522 refers to IWB-3142 for corrective actions.
Article IWB-3142, Acceptance, specifies that a component with a relevant condition is unacceptable for continued service unless the requirements of IWB-3142.2, 3 or 4 have been satisfied. All three options have been considered. IWB-3142.2 is related to acceptance by performing supplemental examinations. This section is about
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 4 of 13 sizing of defects for comparison to ASME criteria to allow leaving a flaw in service.
This option is not applicable to a through-wall condition. IWB-3142.4 is related to determining acceptance by analytical evaluation. This option is not possible because there is not a code-specified methodology for analyzing the condition . Of the three options available for acceptance of a relevant cond ition , a repair/replacement per IWB-3142.3 is the only viable option for addressing the current observed condition.
Although MPS2 can operate without boric acid pumps, maintaining the 'B' boric acid pump available provides additional assurance that the boric acid injection function will remain available for reactivity changes, if needed, until a permanent code repair of the stuffing box cover can be performed . Since delivery of the replacement stuffing box cover is not expected until mid-June, 2017, compliance with the requirements of 10 CFR 50.55a would result in a hardship without a compensating increase in the level of quality or safety.
: 6. Proposed Alternative and Basis for Use 6.1  Proposed Alternative DNC has assessed the condition of the stuffing box cover as structurally acceptable for continued service. Therefore, in lieu of code repair prior to startup, DNC proposes to keep the pump in service with the identified indications until a replacement part is delivered and a permanent code repair can be performed.
DNC will inspect the affected pump stuffing box cover each shift for leakage until the pump is removed from service for repair. The inspection results will be documented. Should leakage increase, an engineering evaluation will be performed to reassess structural integrity and the impact of the leakage on nearby equipment. If structural integrity cannot be maintained, the pump will be isolated.
6.2 Basis for Use During 2R24, the 'B' boric acid pump was disassembled to further evaluate the structural integrity of the stuffing box cover (Figure 1).        The NOE and hydrostatic test reports are provided in Attachment 2.
Liquid penetrant (LP) examinations were performed on both the inside and outside surfaces of the stuffing box cover. LP examination of the outside surface identified two rounded indications, approximately 1/16 of an inch apart, in the area of the observed leak (Figure 2). LP examination of the inside surface identified three rounded indications; two indications were located near one leak off port (in the area of the observed leakage) (Figure 3) , while the third
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 5 of 13 indication was offset approximately 180 degrees near the opposite leak off port.
No recordable indications were identified on the outside of the cover in this area. Table 1 provides the location and size of the indications.
Table 1: B' Boric Acid Pump Stuffing Box Cover LP Indications Indication                    Location            Diameter of bleedout (inches) 1            Outside Surface  - East Side              1/32 2            Outside Surface  - East Side              1/32 3            Inside Surface -  East Side                3/32 4            Inside Surface -  East Side                3/16 5            Inside Surface -  West Side                3/16 DNC attempted to perform volumetric examination of the stuffing box cover using ultrasonic testing (UT). Although the smallest available transducer was used, the UT did not produce any useful information because the UT transducer was not able to maintain suitable surface contact. DNC considered performing radiography. However, due to the dimensions and geometry of the stuffing box cover, DNC determined that examination of the leakage area using radiography was not practical.
DNC performed an informational hydrostatic test of the stuffing box cover. The hydrostatic test was performed at a pressure of 220 psig and held for 10 minutes. Although the test did not result in any measurable leakage, indication of leakage (slight wetting) at two locations was visible through the use of an LP developer. The first location was in the area where the leakage was first observed and the second location was on the opposite side of the cover approximately 180 degrees from the first location. The location where slight wetting was observed on the outside of the stuffing box cover corresponds to the location of the identified indications.
Based on the results of the above inspections, the stuffing box cover pressure boundary leakage is likely due to small casting void defects or porosity that enable a through-wall pathway for leakage. The NOE results (very small rounded indications), the very low leakage at hydrostatic conditions, and the propensity of stainless steel castings to have small amounts of porosity, lead DNC to conclude that porosity is the most likely explanation for what is observed. Alternative explanations have been considered, but determined to be unlikely, as discussed below.
Structural Evaluation Leak Location and Operating Conditions - The location of the leakage is on the portion of the stuffing box cover that surrounds the pump shaft. At this
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 6 of 13 location, the stuffing box seal cover pressure cannot be measured but a typical rule for estimating stuffing box pressures is:
P = (Poutlet - Pinlet) / 4 + Pini et P =stuffing box pressure, psig Poutlet =pump design discharge pressure, psig = 150 psig Pinlet =pump suction pressure, psig = 4.5 psig The pump design discharge pressure is 150 psig and the suction pressure is 4.5 psig. These values give an estimate for the stuffing box pressure of 41 psig using the above rule. For conservatism, 50 psig is assumed.
Material      Performance and        Degradation Potential - The figure at right shows the configuration of the boric acid pump. The boric acid pump has been in service since initial plant operation. The cross-hatched area on the left is the stuffing box cover casting, and the impeller is the cross-hatched component on the right. The stuffing box cover is made from cast type 316 austenitic stainless steel per specification ASTM A351 CF-BM, as shown on the vendor drawing.
Type 316 stainless steel has excellent general corrosion resistance to the boric acid solution that is the process fluid for this pump. Based on testing done for Electric Power Research Institute (Reference 9.2), the general corrosion                                11 rate in the process fluid is too small to measure.
The other internal parts of the pump are made from cast or wrought type 316 stainless steel.
Type 316 stainless steel, either cast or wrought, is not susceptible to pitting or stress corrosion cracking in this environment. The cast version of 316 stainless steel is not susceptible to thermal aging at the low temperature at which this pump operates. Additionally, mechanical loads due to normal operation, including pump vibration, are low and would not be anticipated to result in service induced flaw growth.              With these considerations, it is concluded that there are no active aging degradation mechanisms for this component that would cause initiation and through-wall growth of a planar flaw. The remaining reasonable explanation for the leakage is that there is a leakage pathway via small voids, or porosity, originally present in the cast material. Similar instances of this phenomenon have been documented by other licensees (References 9.3 and 9.4). As discussed below,
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 7 of 13 such small imperfections do not significantly affect the structural integrity of the component.
The absence of an active degradation mechanism also supports the conclusion that the currently observed leak rate will remain nearly constant for the duration of this requested relief.
Structural Integrity - There is no code-specified methodology for evaluating the structural integrity of this type of component when through-wall leakage is detected. However, the stuffing box cover in the area of concern can be conservatively bounded as a cylindrical section, similar to a cylindrical vessel with localized leakage. The Code of Construction for the pump is the draft ASME Code for Pumps and Valves for Nuclear Plants, 1968. The stuffing box cover material is ASTM A351 CF-BM which has an allowable design stress of 17.5 ksi. The inside diameter of this section is approximately 2.5 inches.
Considered as equivalent to a cylindrical vessel, the minimum wall thickness would be calculated per ASME Ill NC-3324 as:
tmin = p RI (S - 0.6 P)
The values for the parameters in this formula are:
P =stuffing box pressure, psig = 50 psig R = radius of the stuffing box = 2.5/2 = 1.25 inches S =stuffing box allowable stress= 0.8 x 17.5 = 14 ksi (including a casting quality factor of 0.8)
The result is tmin = 0.0045 inch.
The actual wall thickness of this section in the area of the observed leakage is not specified on drawings but is estimated to be approximately 0.250 inch based on the minimum wall thickness required for valves by the construction code.      The evaluation result of 0.0045 inch required wall thickness, in comparison to the approximately 0.250 inch estimated actual wall thickness (Figure 4), results in a factor of about 56. This demonstrates that this portion of the pump stuffing box cover is not challenged by the pump stuffing box pressure. Additionally, this portion of the stuffing box cover is not required to withstand any significant mechanical loading. This portion of the casting supports only the mechanical shaft seal. The pump shaft is supported independently of the stuffing box cover and seismic loading from the shaft, impeller, and piping nozzles are transferred through the pump frame adaptor and pump casing to anchorage feet attached to the pump casing. The loads do not pass through this portion of the stuffing box cover. Thus the minimum wall thickness calculation reasonably demonstrates the structural integrity of the pump stuffing box cover in the area of the observed leakage.
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 8 of 13 Functionality - The above structural integrity evaluation supports the conclusion that the pump is capable of performing its intended function of transferring concentrated boric acid from the boric acid storage tank to the suction of the charging pumps and will retain this capability for the duration of the requested relief. The overall mechanical integrity of the pump will be maintained such that the pump will be able to generate sufficient head for the required flow, and since the pressure boundary is maintained, there would be no significant diversion of boric acid intended for injection into the charging pump suction.
Conclusion ASME Section XI requires the defect be corrected prior to returning the affected component to service. However, compliance with the requirements of 10 CFR 50.55a would result in a hardship without a compensating increase in the level of quality and safety pursuant to 10 CFR 50.55a(z)(2) . The structural integrity of the stuffing box cover cannot be demonstrated in accordance with a code-specified methodology. However, based on LP examination , hydrostatic testing and comparison with typical ASME code design rules, it is concluded that there is reasonable assurance that the structural integrity and functional requirements of the pump will be maintained during the requested period of relief. Delivery of a new stuffing box cover is not expected until mid-June 2017. Therefore, the continued availability of the 'B' boric acid pump is needed to provide defense-in-depth for reactivity control until a permanent code repair of the stuffing box cover can be performed.
: 7. Duration of Proposed Alternative This relief is requested to be effective upon approval and until a permanent code repair of the boric acid pump stuffing box cover can be performed during Cycle 25.
Delivery of the stuffing box cover is expected in mid-June. A permanent code repair will be performed as soon as practical after receipt of the part, but no later than startup from the next refueling outage.
: 8. Precedent Email from R. Guzman to W. Craft - Millstone Power Station Unit 2, Verbal Authorization by the NRR staff - Relief Request No. RR-04-25 (CAC No. MF9497) ,
dated March 29 , 2017 (ADAMS Accession No. ML17088A719).
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 9 of 13
: 9. References 9.1 Dominion Nuclear Connecticut Inc., Millstone Power Station Unit 2, ASME Section XI Relief Request RR-04-25 , dated March 29, 2017 (ADAMS Accession No. ML17090A110).
9.2 2012 EPRI Technical Report: Materials Reliability Program: Boric Acid Corrosion Guidebook, Revision 2: Managing Boric Acid Corrosion Issues at PWR Power Stations (MRP-058, Rev 2).
9.3 NRG letter from J. Quichocho (USNRC) to W. Gideon (CP&L), dated December 12, 2012, "H. B. Robinson Steam Electric Plant, Unit No. 2 - Relief Request-07 from Immediate ASME Code Repair of Refueling Water Storage Tank Drain Valve (Safety lnjection-837) for Fifth10-year lnservice Inspection Program Plan (TAC NO. ME9747)." [ADAMS Accession Number ML12325A612]
9.4 NRG Letter from J. B. Martin (USNRC) to C. A. Schrock (WPSC) dated November 5, 1993, related to Notice of Enforcement Discretion associated with Residual Heat Removal Pump Casting Void . (As identified in WPSC letter from C. A. Shrock to USNRC, dated December 6, 1993, "Reportable Occurrence 93-019-00").
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 10 of 13 Figure 1
'B' Boric Acid Pump Stuffing Box Cover
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 11 of 13 Figure 2 Rounded Indications on Outside Surface of Stuffing Box Cover (In area where leakage was observed)
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 12 of 13 Figure 3 Rounded Indications on Inside Surface of Stuffing Box Cover
 
Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 13 of 13 Figure 4 Photo Showing Wall Thickness of Stuffing Box Cover
 
Serial No. 17-187 Docket No. 50-336 ATTACHMENT 2 NON-DESTRUCTIVE EXAMINATION AND HYDROSTATIC TEST REPORTS MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.
 
Serial No. 17-187 Docket No. 50-336 Attachment 2, Page 1 of 12 Liquid Penetrant Examination (Page 1 of l)
                                                      -*******                                                                                    * -- *~ -                                                ---*--
Site/Unit: Millstone                                                    Procedure: ER-AA-NDE-PT-301                                                        Outage No.: 2R24 Summary No.: NI.A                                                        Pi-ocedure Rev.: 7                                                                .Repott No.: NIA Workscope: .E11g Information                                              Work Order No.; 53103060177                                                        Page: I                of    <{*
Code: N/A                                                                CatJJtem: NIA                                                                      Location: -5' Aux Bdg Drawing No.: 25203-29163 SH 5                                           
 
== Description:==
Pl9B Stuffing Box Cover ID Exam System JD: M2Pl9B Component JD: Pl 9B Stuffing Box Cover
                                          .....                                                                                --***********                  I"'U!"""~* 0 Size/Length: 0 NJ.A.
NIA Limitations: NI A Light Meter Mfg.: Spectroline                                            Serial No.: MTE-02951                                                              Illumination: > 100 fc Temp. Tool Mfg.: KTA Tator                                          ! Serial No. :.M"11i=o~8                                                            Surface Temp.: 72.5 op Comparator Block Temp.: Side ANIA &deg;F SideB NIA &deg;F
                                                        .. .. ..........i...
IReso lution; Nl~**-***                                            *-
ISurface Condition: Machined f---
Lo/Wo Location: C/L of1hreaded plug I Top edge of Cover
                            ~--- - ---* ~--------~----------~--------,
Cleaner                                            Penetrant                                                .Remover                                    Developer            1 Brand                      Magnaflux                                      Magnat:hrx                                                  Magnaflux                                        Magnatlux
                                                                                                        ***********************--****-1-- - -- - - - -- - t - - - - -*                                    -    ---l Type                      SKC-S                                          SKL-SP2                                                    SKC-S                                            SKD-S2 Batch No.                  15El5K                                        13JIOK                                                      12G04K                                          13G07K
- -*******-**-----+--- - -- - - - + -
Time                      Evap. 4min                                      Dwell 15min                                                Evap. I min                                    . Develop 10 min
!----~- *-*-- **** -------'---------***- * **-+----------~-----*
Time Exam Started:                              09:27                                                      Time Exam Completed:                              10:10 Indication                Loe          Loe          Diameter                  Length                Type                                                            Remarks 1_ _N          ~'=  o ~.--+---"L"---+---"      w.__+--****- -                    - --+-"""Ri""'IJ"'"                , -+- - -- - * - - - -*
                          . !['J2C<..l . -;i\fy,"        3 ;):.)''                  ...lfl\
            '.2...          '.}-Bo-> ~"'!~'            .?:D~'  -~--+----+-          t-.l/A              ~--.....t:;~                        $ \ J.<. t'\~o..k            :t:D o(' co'\Je.Jr
_".:>            l/~ ew ?..'/?i''
0
                                                                                      ....if A 3..N~t                                                              "'1e.::;,"    ~id.<-      ...i    O>\*      :t::t>.. .Qf_c~O\J~e~((
                                                                                                                                                                                                  ~-------<
Comments: Examined machined JD of stuifmg box cover Results: NR! 0 RI                  0    Eval ~
Percent of Coverage Obtained >90%: NIA                                                                                        R.evicwed Previous Date: NIA Examiner                        Level        Siguatuni                      Date                                        Reviewer                                                    Date II                                                      Lj l'l        11 Examiner                        Level      'S gnatw*                        Dale NIA Other                          Level        Signature                      Date                                                                      Sig11ature                    Date NIA
 
Serial No. 17-187 Docket No. 50-336 , Page 2 of 12
 
Serial No. 17-187 Docket No. 50-336 , Page 3 of 12
 
Serial No. 17-187 Docket No. 50-336 , Page 4 of 12
 
Serial No. 17-187 Docket No. 50-336 Attachment 2 , Page 5 of 12 Liquid Penetrant Examination (J'agc I of I )
Site/Unit: Millstone                                                                                Procedure: ER-AA-NDE-PT-30 1                                  Outage No.: 2R24 Summary No.: NJ.A                                                                                  Procedure Rev.: 7                                            Repo1tNo.: N/A
  ..........___.._..__.........._ ........._____--;,__--- -- -- - - - -- -t - - - - - - - - - ------1 Wo!'.kscope: Eng huorr.nntion                                                                      Work Order No.: 53103060177                                  Page: I            of        L\
Code: N/A                                                                                          Cat/Item: NIA                                              J~~3-~o_n_:_*:i_**_A_ux_*_B_d_g_ _ _ __ ___.
Drawing No.: 25203-29163 SH 5                                                                     


== Description:==
== Description:==
Pl 9B Stuffing Box Cover OD Exam
        *** ** ** ***** ****************** * ************* * **- * ------~--------------..------------*-*-
System JD: M2Pl9B                                                                                                                                                Mat/111ickncss:            0              N JA
                                                                          ......................................- -- -- - - - - - - - - - + - -- -- - - - -- - - ---<
Component JD: Pl9B Sni.ffing Box Cover                                                                                                                          I Size/Length: 0                              ..J/A.
>---------------------------*-* --* ---*-~----------------
Limitations: NIA 1
Light Meter Mfg.: Spectrolinc                                                                      Serial No. : MTE-02951                                        l1Jumination; > 100 fc Temp. Tool Mfg.: KTA Tator                                                                    l Serial No.: MTE-01887                                            Surface Temp.: 72.5 &deg;F t---------------L----------~-----'------*----- --*****-**** * *-------<
Comparator Block Temp. : Side A NIA &deg;F Side B NIA &deg;F                                                                                                  IResolution: NIA Lo/Wo Location: Cl1, of threaded plug i Top edge of Cover                                                                      ISurface Condition: As cast with ground areas
                                                                                                                                    **--**-***  ---*-****---**-                            *1- - -- - - - -- -
* Cleaner                                            Penetraut                                  Remover                    i                    Developer Brand
* Magna11ux                                            ! Magnatlux I
[ Magnafiux I
Magnaflux Type                                          SKC-S                                                  SKL-SP2                                SKC-S                                          SKD-S2 Batch No.                                      15El5K                                                J3JJOK                                  12G04K                                          13G07K Tinle                                        Evap. 3 min                                            Dwcll 15 min                            Evap. J min                                    Develop lO min Time b'xam. Started:                                    10:25                                  Time Exam Completed:                            11:10 Indication                                    Loe            Loe          Diameter                      Length        Typt:                                          Remarks No.                                  L            w                                                        R/L
  - - - - * -**                                3.l:PS!.iu ~f)J.~                I/;;,::/'                      ~IA          R
                  ?....                            ;;.Q'a:w -;i'/~"            \ ?;,";/'                      i-l/A        R Comments: Examined at areas of ID indications
                                                                                                                                                                                                                                        .. l
,__R_esu_l_ts_:_N_RI                    _.. _ D_R_1D_ E_..v_a1_18J        _ _ _ __ _______ .....................................................- ...................................._.________......................................__..__ ~
Percent of Coverage Obtained >90%: N/A                                                                                              Reviewed Previous Date: NIA Date                      Reviewer                    Signatt1reJi}            Date l .( 19,)11 1
Examiner                                                                                                Date l NIA
'l Other                                                Level        Signature                              Date NIA
  .............................................. ..*--------------~-------------------~
Serial No. 17-187 Docket No. 50-336 , Page 6 of 12
Serial No. 17-187 Docket No. 50-336 , Page 7 of 12
Serial No. 17-187 Docket No. 50-336 Attachment 2, Page 8 of 12 West Side Plug a J
Serial No. 17-187 Docket No. 50-336 Attachment 2, Page 9 of 12 Attachment 1 Pressure Test Parameter Worksheet (Sheet 6 of 6)
Type of 1est:                                        Normal F luid:
Step                                                          Parameter s 1.3      Inspection Requires VT-2 qualified examiner ? .(circle one)                  YES          NO 1.4      D esign pressure 1.5      Hydrostatic Test P ressure (HTP) 1.6      Pressure gauge range limits;                                                                  OD 1.7 1.8      Tust Medium and Source 1.9 1.9.3      Test hold time (Insulated 4 hours, Non -insulated 10 m inutes, or other)                    0 Ve.rtical distance between lowest p ortion of hydros tatic test boundary and test pressure gauge (negative if gauge is higher than lowest point; positive if gauge is lower than lowest point)        (ti. Li) =            (feet)  O 1.10 Vertical distance between highest portion of hydrostatic test boundary and test pressure gauge (negative if gauge is higher than highest point; positive if gauge is lower than highest point) (ti.        Lz) =            (feet)  0 1.11.a Max Pressure limit = 1.06 x HTP + (t. Li                x 0.4335) =    J.. l...&&deg; or Design document Min Pressure limit= H TP + (ti. Lz x 0.4335)              =    J 'b1 , 5 or Design document 1.11.b If Min Pressure is greater than M ax Pressure,                /J./
Min Pressure = 0.94 x Max Pressure                              I n11 Vertical distance, relief valve to lowest point in test boundary (nega tive if relief valve is above low point of test bow1dary;
: t. L:> =          (feet) NJ 1.12      positive if relief valve is below low point of test boundary)                                          Ill Relief valve setting= 1.06 x HTP + (t. L3 x 0.4335)                  =
*---+* -* . ,..                                  or D esign documen t Reiiei'-;a1~e *g;;ggfug Ci~;;r~;c;~*mo<lifi~~tioii ~eq uired. ~~--~
1.14      Gagging device or modification within test boundaries.
Separate WO 's Worksheet Prep ared By:                                                                                    D ate :
Level of Use                                  ;.
CMP 727 Reference                                            * ..
STOP .      THINK          ACT        REVIEW          Rev. 001 -00 23 of 31
Serial No. 17-187 Docket No. 50-336 Attachment 2, Page 10 of 12 I'                f' 'I Attachment 2 Hydrostatic Test Data Sheet (Sheet 1 of 1)
SECTION A: Responsible Engineer to Complete D AS ME-XI SHOP TEST                        ~ NON-AS ME- XI SHOP TEST          D NoN- ASME-Xi IN-PlANT TEST IXJ  COMPONENT                                                    D    PIPING Test Medium:                              fl                  Test pressures:
1--~~~~~-.J.            .......~..t.K...;'-'l......,_~~~~--1 Medium source:                                                Min: (  Jg 71 S          Max: (    .(.l$
Test pressure nominal:                                        Pressure gauge calculated range:
Test hold time:                                                Min: (  3 3 71 5 . )    Max: (    9(j 0 Relief valve location:                                        Relief valve setting:    f1iJA SECTION B: Examiner to Complete (VT-2 certified if "YES" in 1.3, Attachment 1) 1; Level: "][
Examiner signature:                                                              Date:    &#xa5;, J. o 17 PART C:        *Responsible Engineer to Complete Disposition:
T                                                0 Name (print):
1 Signature:                                                                        Date:
PART D:        ANll Review (if ASME piping or component)
Name (print) :
Signature:                                                                        Date:
f.
Level of Use                                                                      CMP727 Reference                  ~.sf~w;                                              Rev. 001-00 t>~--~~.~ ~,
v        "<;;
24 of 31
Serial No. 17-187 Docket No. 50-336 , Page 11 of 12 04 20 2017      ~


Components
Serial No. 17-187 Docket No. 50-336 , Page 12 of 12 04 20 2017       ~
: Millstone Power Station Unit 2 (MPS2) 'B' boric acid pump. The 'B' boric acid pump stuffing box cover is a casting o f type 316 austenitic stainless steel per American Society fo r Testing and Materials (ASTM) A351 CF-8M. 2. Applicable Code Edition and Addenda MPS2 is currently in the fourth 10-year inservice inspection (ISi) interva l, which started on April 1 , 2010 , and ends on March 31 , 2020. The ASME Section XI , 2004 Edition (No Addenda) applies to the ISi program. 3. Applicable Code Requirement The ASME Code requirements for this relief request are those associated with Section XI , 2004 Edition , No Addenda , (Reference 8.1) and contained in Article IWB-3142, Acceptance.
                      --t--}}
: 4. Background The 'B' boric acid pump is one of two redundant pumps used for boron injection in t o the reactor coolant system. The function of the boric acid pumps is for reactivity control , but the pumps are not credited in the Final Safety Analysis Report , Chapte r 14 accident analyses. The design and normal operat i ng parameters for the 'B' boric acid pump are provided below. Design pressure = 150 psig Design temperature=
250 degrees Fahrenheit Operating discharge pressure = 112 psig Operating suction pressure = 4.5 psig Operating temperature= ambient temperature (110 degrees Fahrenheit)
Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 2 of 1 3 Although MPS2 was designed and licensed to the GDC as issued on July 11 , 1967 , DNC has attempted to comply with the intent of the newer General Design criteria to the extent possible, recognizing previous design commitments.
MPS2 meets the intent of GDC 26, Reactivity Control System Redundancy and Capability, by employing two independent systems for controlling reactivity changes , including boric acid shim control , of which the boric acid pumps are a part. These systems compensate for long term reactivity changes such as those associated with fuel burnup , variation in the xenon and samarium concentrations , and plant cooldow n and heatup. The 'B' boric acid pump provides a redundant means of delivering boric acid to the suction of the charging pumps to control reactivity during normal powe r operation and for such events as a Technical Specifications required cooldown to cold shutdown.
On February 28 , 2017 , during a visual (VT-2) examination of the 'B' boric ac i d system, dry boric acid residue was identified on the pump stuffing box cover. The source of the boric acid could not be i dentified. This condition was entered into the corrective action program. During the following sh i ft , the boric acid residue wa s cleaned and the pump was run for two hours in an attempt to determine the leak location and leak rate. No evidence of leakage was observed by the plan t equipment operator who was stationed at the pump during the two-hour run. On March 1 , 2017 , a follow-up ISi walkdown was performed and dry boric ac i d residue was found at the same location, but in a smaller quantity.
The pump was declared non-functional and corrective action was initiated to identify the source o f the leak. On March 2 , 2017 , the 'B' boric acid pump was tagged out , but not drained , to support an informational liquid penetrant (LP) examination. The examination found no relevant or recordable indications.
Following the LP examination , the 'B' boric acid pump was cleaned and then run for an additional time. After 10 minutes , a small accumulation of boric acid residue appeared as a wet , translucent spot. Afte r 1.5 hours of run time , the wet spot had increased in size to about 1/8 inch in diameter.
Although a measurable leak rate could not be determined , growth of the wet spot confirmed the presence of a through-wall leak. The pump was subsequently isolated on March 9 , 2017. Because of limited access and complex surface geometry, direct volumetr i c examination of the leakage location from the outside surface of the assembled pump was not possible. However , based on an informational LP examination and visual examination of leakage during an extended pump run , DNC concluded the boundary leakage was likely the result of small voids or porosity present in the origina l stainless steel casting material.
DNC researched the original purchase order for the pump to identify initial testing associated with the boric acid pump. The pump was constructed in accordance with the draft ASME Code for Pumps and Valves for Nuclear Power , dated November Serial No. 17-187 Docke t No. 50-336 Attachment 1 , Page 3 of 13 1968, as Class 2, and Combustion Engineering specification 18767-PE-404 , Revision 1 , dated February 9 , 1972. The Combustion Engineering specification refers to the ASME code for testing requirements.
Section B of the draft ASME code contains the requirements for Class 2 pumps and valves. Article 23, sub-article 2314 specifies special requirements related to Class 2 components. Normally, this sub-article would require that radiography be performed for a cast product. However , sub-article 2314 identifies that the specia l requirements do not apply to materials for pumps and valves with inlet piping connections of four inches and less in nominal pipe size unless otherwise noted in the design specification.
The inle t piping to the boric acid pump is less than four inches and the design specification d i d not invoke a radiography requirement for this pump. Initial testing did include an LP examination and a hydrostatic test and the examination and test had satisfactory results. Following discovery of the through-wall leak, DNC submitted a purchase order to the pump vendor for a new stuffing box cover. Due to the long lead time to fabricate a replacement stuffing box cover , a code repair of the 'B' boric acid pump was not possible prior to the scheduled shutdown date for 2R24. However , based on engineering assessment of the as-found condition, DNC had high confidence tha t structural integrity of the stuffing box cover would be maintained for the duration of Cycle 24 operat i on and execution of the plant shutdown and core offload for 2R24. Therefore , on March 29 , 2017 , DNC requested relief (Reference 9.1) from IWB-3142 of Section XI of the Code to provide continued availability of the 'B' boric acid pump for the remainder of Cycle 24 operation and execution of the plant shutdown and core offload for 2R24. Compliance with the requirements of 10 CFR 50.55a would have resulted in a hardship without a compensating increase in the level of quality o r safety. Verbal approval of the relief request was granted by the NRC the same day (ADAMS Accession No. ML 17088A719).
The stuffing box cover on the 'B' boric acid pump has since been removed for furthe r characterization of the through-wall flaw. Based on LP examination and hydrostatic testing , DNC has assessed the stuffing box cover as structurally acceptable fo r continued service. Details of that evaluation are provided in Section 6 below. 5. Reason for Request The 2004 ASME Section XI code was reviewed for acceptance standards associated with the stuffing box cover leak. Table IWC-3410-1 , Acceptance Standards, indicates for pressure retaining components (examination category C-H), the acceptance standard is IWC-3516. IWC-3516 refers to IWB-3522.
IWB-3522 refers to IWB-3142 for corrective actions. Article IWB-3142 , Acceptance , specifies that a component with a relevant conditio n is unacceptable for continued service unless the requirements of IWB-3142.2 , 3 or 4 have been satisfied.
All three options have been considered.
IWB-3142.2 is related to acceptance by performing supplemental examinations.
This section i s abou t Seria l No. 17-18 7 Docket No. 50-336 Attachment 1 , Page 4 of 13 sizing of defects for comparison to ASME criteria to allow leaving a flaw in service. This option is not applicable to a through-wall condition.
IWB-3142.4 is related to determining acceptance by analytical evaluation.
This option is not possible because there is not a code-specified methodology for analyzing the condition. Of the three options available for acceptance of a relevant cond i tion , a repair/replacement per IWB-3142.3 is the only viable option for addressing the current observed condition.
Although MPS2 can operate without boric acid pumps , maintaining the 'B' boric acid pump available provides additional assurance that the boric acid injection function will remain available for reactivity changes, if needed , until a permanent code repair of the stuffing box cover can be performed. Since delivery of the replacement stuffing box cover is not expected until mid-June , 2017 , compliance with the requirements of 10 CFR 50.55a would result in a hardship without a compensating increase in the level of quality or safety. 6. Proposed Alternative and Basis for Use 6.1 Proposed Alternative DNC has assessed the condition of the stuffing box cover as structurally acceptable for continued service. Therefore, in lieu of code repair prior to startup , DNC proposes to keep the pump in service with the identified indications until a replacement part is delivered and a permanent code repair can be performed.
DNC will i nspect the affected pump stuffing box cover each shift for leakage until the pump is removed from service for repair. The inspection results will be documented.
Should leakage i ncrease , an engineering evaluation will be performed to reassess structural integr i ty and the impact of the leakage o n nearby equipment.
If structural integrity cannot be maintained , the pump will be isolated.
6.2 Bas i s for Use During 2R24 , the 'B' boric acid pump was disassembled to further evaluate the structural integrity of the stuffing box cover (Figure 1 ). The NOE and hydrostatic test reports are provided in Attachment
: 2. Liquid penetrant (LP) examinations were performed on both the inside and outside surfaces of the stuffing box cover. LP examination of the outside surface identified two rounded indications , approx i mately 1/16 of an inch apart , in the area of the observed leak (Figure 2). LP examination of the inside surface identified three rounded indications
; two indications were located nea r one leak off port (in the area of the observed leakage) (Figure 3), while the third Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 5 of 13 indication was offset approximately 180 degrees near the opposite leak off port. No recordable indications were identified on the outside of the cover in this area. Table 1 provides the location and size of the indications.
Table 1: B' Boric Acid Pump Stuffing Box Cover LP Indications Indication Location Diameter of bleedout (inches) 1 Outside Surface -East Side 1/32 2 Outside Surface -East Side 1/32 3 Inside Surface -East Side 3/32 4 Inside Surface -East Side 3/16 5 Inside Surface -West Side 3/16 DNC attempted to perform volumetric examination of the stuffing box cover using ultrasonic testing (UT). Although the smallest available transducer was used, the UT did not produce any useful information because the UT transducer was not able to maintain suitable surface contact. DNC considered performing radiography.
However, due to the dimensions and geometry of the stuffing box cover, DNC determined that examination of the leakage area using radiography was not practical.
DNC performed an informational hydrostatic test of the stuffing box cover. The hydrostatic test was performed at a pressure of 220 psig and held for 10 minutes. Although the test did not result in any measurable leakage, indication of leakage (slight wetting) at two locations was visible through the use of an LP developer.
The first location was in the area where the leakage was first observed and the second location was on the opposite side of the cover approximately 180 degrees from the first location.
The location where slight wetting was observed on the outside of the stuffing box cover corresponds to the location of the identified indications.
Based on the results of the above inspections, the stuffing box cover pressure boundary leakage is likely due to small casting void defects or porosity that enable a through-wall pathway for leakage. The NOE results (very small rounded indications), the very low leakage at hydrostatic conditions, and the propensity of stainless steel castings to have small amounts of porosity, lead DNC to conclude that porosity is the most likely explanation for what is observed.
Alternative explanations have been considered, but determined to be unlikely, as discussed below. Structural Evaluation Leak Location and Operating Conditions
-The location of the leakage is on the portion of the stuffing box cover that surrounds the pump shaft. At this Serial No. 17-187 Docket No. 50-336 Attachment 1, Page 6 of 13 location, the stuffing box seal cover pressure cannot be measured but a typical rule for estimating stuffing box pressures is: P = ( P outlet -Pinlet) / 4 + Pini et P =stuffing box pressure, psig Poutlet =pump design discharge pressure, psig = 150 psig Pinlet =pump suction pressure, psig = 4.5 psig The pump design discharge pressure is 150 psig and the suction pressure is 4.5 psig. These values give an estimate for the stuffing box pressure of 41 psig using the above rule. For conservatism, 50 psig is assumed. Material Performance and Degradation Potential
-The figure at right shows the configuration of the boric acid pump. The boric acid pump has been in service since initial plant operation.
The cross-hatched area on the left is the stuffing box cover casting, and the impeller is the cross-hatched component on the right. The stuffing box cover is made from cast type 316 austenitic stainless steel per specification ASTM A351 CF-BM, as shown on the vendor drawing. Type 316 stainless steel has excellent general corrosion resistance to the boric acid solution that is the process fluid for this pump. Based on testing done for Electric Power Research Institute (Reference 9.2), the general corrosion 11 rate in the process fluid is too small to measure. The other internal parts of the pump are made from cast or wrought type 316 stainless steel. Type 316 stainless steel, either cast or wrought, is not susceptible to pitting or stress corrosion cracking in this environment.
The cast version of 316 stainless steel is not susceptible to thermal aging at the low temperature at which this pump operates.
Additionally, mechanical loads due to normal operation, including pump vibration, are low and would not be anticipated to result in service induced flaw growth. With these considerations, it is concluded that there are no active aging degradation mechanisms for this component that would cause initiation and through-wall growth of a planar flaw. The remaining reasonable explanation for the leakage is that there is a leakage pathway via small voids, or porosity, originally present in the cast material.
Similar instances of this phenomenon have been documented by other licensees (References 9.3 and 9.4). As discussed below, Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 7 of 13 such small imperfections do not significantly affect the structural integrity of the component.
The absence of an active degradation mechanism also supports the conclusion that the currently observed leak rate will remain nearly constant for the duration of this requested relief. Structural Integrity
-There is no code-specified methodology for evaluating the structural integrity of this type of component when through-wall leakage is detected.
However, the stuffing box cover in the area of concern can be conservatively bounded as a cylindrical section, similar to a cylindrical vessel with localized leakage. The Code of Construction for the pump is the draft ASME Code for Pumps and Valves for Nuclear Plants, 1968. The stuffing box cover material is ASTM A351 CF-BM which has an allowable design stress of 17.5 ksi. The inside diameter of this section is approximately 2.5 inches. Considered as equivalent to a cylindrical vessel, the minimum wall thickness would be calculated per ASME Ill NC-3324 as: tmin = p RI (S -0.6 P) The values for the parameters in this formula are: P =stuffing box pressure, psig = 50 psig R = radius of the stuffing box = 2.5/2 = 1.25 inches S =stuffing box allowable stress= 0.8 x 17.5 = 14 ksi (including a casting quality factor of 0.8) The result is tmin = 0.0045 inch. The actual wall thickness of this section in the area of the observed leakage is not specified on drawings but is estimated to be approximately 0.250 inch based on the minimum wall thickness required for valves by the construction code. The evaluation result of 0.0045 inch required wall thickness, in comparison to the approximately 0.250 inch estimated actual wall thickness (Figure 4), results in a factor of about 56. This demonstrates that this portion of the pump stuffing box cover is not challenged by the pump stuffing box pressure.
Additionally, this portion of the stuffing box cover is not required to withstand any significant mechanical loading. This portion of the casting supports only the mechanical shaft seal. The pump shaft is supported independently of the stuffing box cover and seismic loading from the shaft , impeller, and piping nozzles are transferred through the pump frame adaptor and pump casing to anchorage feet attached to the pump casing. The loads do not pass through this portion of the stuffing box cover. Thus the minimum wall thickness calculation reasonably demonstrates the structural integrity of the pump stuffing box cover in the area of the observed leakage.
Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 8 of 13 Functionality
-The above structural integrity evaluation supports the conclusion that the pump is capable of performing its intended function of transferring concentrated boric acid from the boric acid storage tank to the suction of the charging pumps and will retain this capability for the duration of the requested relief. The overall mechanical integrity of the pump will be maintained such that the pump will be able to generate sufficient head for the required flow , and since the pressure boundary is maintained , there would be no significant diversion of boric acid intended for injection into the charging pump suction. Conclusion ASME Section XI requires the defect be corrected prior to returning the affected component to service. However , compliance with the requirements of 10 CFR 50.55a would result in a hardship without a compensating increase in the level of quality and safety pursuant to 10 CFR 50.55a(z)(2). The structural integrity of the stuffing box cover cannot be demonstrated in accordance with a specified methodology.
However , based on LP examination , hydrostatic testing and comparison with typical ASME code design rules, it is concluded that there is reasonable assurance that the structural integrity and functional requirements of the pump will be maintained during the requested period of relief. Delivery of a new stuffing box cover is not expected until mid-June 2017. Therefore, the continued availability of the 'B' boric acid pump is needed to provide in-depth for reactivity control until a permanent code repair of the stuffing box cover can be performed.
: 7. Duration of Proposed Alternative This relief is requested to be effective upon approval and until a permanent code repair of the boric acid pump stuffing box cover can be performed during Cycle 25. Delivery of the stuffing box cover is expected in mid-June.
A permanent code repair will be performed as soon as practical after receipt of the part, but no later than startup from the next refueling outage. 8. Precedent Email from R. Guzman to W. Craft -Millstone Power Station Unit 2, Verbal Authorization by the NRR staff -Relief Request No. RR-04-25 (CAC No. MF9497), dated March 29 , 2017 (ADAMS Accession No. ML 17088A719). 
: 9. References Serial No. 17-18 7 Docket No. 50-336 Attachment 1 , Page 9 of 13 9.1 Dominion Nuclear Connecticut Inc., Millstone Power Station Unit 2, ASME Section XI Relief Request RR-04-25 , dated March 29 , 2017 (ADAMS Accession No. ML 17090A 110). 9.2 2012 EPRI Technical Report: Materials Reliability Program: Boric Acid Corrosion Guidebook , Revision 2: Managing Boric Acid Corrosion Issues at PWR Power Stations (MRP-058 , Rev 2). 9.3 NRG letter from J. Quichocho (USNRC) to W. Gideon (CP&L), dated December 12 , 2012 , " H. B. Robinson Steam Electric Plant , Unit No. 2 -Relief Request-07 from Immediate ASME Code Repair of Refueling Water Storage Tank Drain Valve (Safety lnjection-837) for Fifth10-year lnservice Inspection Program Plan (TAC NO. ME9747)." [ADAMS Accession Number ML 12325A612]
9.4 NRG Letter from J. B. Martin (USNRC) to C. A. Schrock (WPSC) dated November 5 , 1993 , related to Notice of Enforcement Discretion associated with Residual Heat Removal Pump Casting Void. (As identified in WPSC letter from C. A. Shrock to USNRC, dated December 6 , 1993 , "Reportable Occurrence 93-019-00").
Figure 1 Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 10 of 13 'B' Boric Acid Pump Stuffing Box Cover Figure 2 Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 11 of 13 Rounded Indications on Outside Surface of Stuffing Box Cover (In area where leakage was observed)
Figure 3 Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 12 of 13 Rounded Indications on Inside Surface of Stuffing Box Cover Figure 4 Serial No. 17-187 Docket No. 50-336 Attachment 1 , Page 13 of 13 Photo Showing Wall Thickness of Stuffing Box Cover ATTACHMENT 2 Serial No. 17-187 Docket No. 50-336 NON-DESTRUCTIVE EXAMINATION AND HYDROSTATIC TEST REPORTS MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.
Serial No. 17-187 Docket No. 50-336 Attachment 2, Page 1 of 12 -******* Site/Unit:
Millstone Summary No.: NI.A Workscope: .E11g Information Code: N/A Liquid P e n e trant Ex a m inati o n (Page 1 of l) Procedure:
ER-AA-NDE-PT-3 01 Pi-ocedure Rev.: 7 -******---. Work Order No.; 53103060177 Cat J Jtem: NIA ---*--Outage No.: 2R24 *-******** .Repott No.: NIA Page: I of <{* Location: -5' Aux Bdg *-***-***--.. Drawing No.: 25203-29163 SH 5 Description
: Pl9B Stuffing Box Cover ID Exam ... -**-**-***---I 0 System JD: M2Pl9B NJ.A. ...... --*********** ********-Component JD: Pl 9B Stuffing Box Cover Size/Length:
0 NIA *-*********-*----------**-**-* **-Limitations:
N I A Light Meter Mfg.: Spectroline Serial No.: MTE-0 2 951 Illumination
: > 100 fc Temp. Tool Mfg.: KTA Tator ! Serial No.: Surface Temp.: 72.5 op ..............
i... I Reso l ution;
*-Comparato r Block Temp.: Side AN I A &deg;F SideB N I A &deg;F f-----I Surface Condition:
Machined *--**-Lo/Wo Location:
C/L of1hreaded plug I Top edge of Cover *--
Cleaner Penetrant .Remover Developer 1 Brand Magnaflux Magnat:hrx Magnaflux Magnatlux
***********************--****-1-----------t-----* ----l Type SKC-S SKL-SP2 SKC-S SKD-S2 Batch No. 15El5K 13JIOK 12G04K 13G07K --*******-**-----+---------+-Time Evap.4min Dwell 15min Evap. I min . Develop 10 min Time Exam Started: 09:27 Time Exam Completed:
10: 1 0 Indication Loe Loe Diameter Length Type Remarks 1 __
--+---"L"---+---" w.__+--****-----+-"""Ri""'IJ"'" ,-+-----* ----* [' .. ! J2C<..l. -;i\fy," 3 ;):.)'' ...lfl\ '.2... '.}-Bo->
.. t-.l/A .....
$\J.<.
:t:D o(' co'\Je.Jr
_".:> ?..'/?i''
....if A "'1e.::;,"
...i O>\* :t::t>. ..
Comm e nts: Examined machined JD of stuifmg box cover Results: NR! 0 RI 0 Eval Percent of Coverage Obtained >90%: N I A R.evicwed Previous Date: N I A Examiner Level Siguatuni Date Reviewer Date II Lj l'l 11 E xaminer Level 'S gnatw* Dal e N I A Other Level Signature Date Sig11ature Date N I A ..............
............ ***----------------'
Serial No. 17-187 Docket No. 50-336 Attachment 2 , Page 2 of 12 Serial No. 17-187 Docket No. 50-336 Attachment 2 , Page 3 of 12 Serial No. 17-187 Docket No. 50-336 Attachment 2 , Page 4 of 12 Serial No. 17-1 87 Docket No. 50-3 3 6 Attachment 2 , Page 5 o f 12 Site/Unit:
Millstone S um mary No.: N J.A Liq u i d Penetran t Examinati o n (J'agc I of I) Procedure: ER-AA-N D E-PT-30 1 Procedure Rev.: 7 Outage No.: 2R2 4 Repo1tNo.:
N/A ..........
___ .. _ .. __ .......... _ ......... _____ --;,__-------------t----------
-----1 Wo!'.kscope
: E ng huorr.nntion Work Order No.: 53103060177 Page: I of L\ Code: N/A Cat/Item:
N I A  "______ __. Drawing No.: 2 5 203-29163 SH 5 D e s cr ipti o n: Pl 9B Stuffing Box Cover OD E xam System JD: M2Pl9B Mat/111ickncss:
0 N J A ......................................
--------------+--
-------------< I Size/Length: 0 ..J/A. Componen t JD: Pl 9B Sni.ffing Box Cover Limitations:
N I A 1 Light Meter Mfg.: Spectrolinc l1Jumination;
> 100 fc Temp. Tool M fg.: KTA Tator Surface Temp.: 72.5 &deg;F Seria l No.: MTE-02951 l Serial No.: MTE-01887 Comparator Block Temp.: Side A N I A &deg;F Side B NIA &deg;F I Resolution
: N I A Lo/Wo Locat ion: Cl1 , o f threaded p lug i Top edge of Cover I Surface Cond i tion: As ca s t with ground areas **--**-*** ---*-****---**-
*1----------* Cleaner Penetraut R emover i Deve l op er
* Magna11ux
! Magnatlux
[ Magnafiux Magnaflux I I Brand Type SKC-S SKL-SP2 SKC-S SKD-S2 Batch No. 15El5K J3JJOK 1 2 G04K 13G07K Tinle Evap. 3 min D wcll 15 min E vap. J min Develop lO min !------'----
---*---.. -___ .. _ .. ___ _ Time b'xam. Started: 10:25 Time Exam C omplete d: 11:10 In dicati o n Loe Loe D iamete r Length Typt: Remarks No. L w R/L 3.l:PS!.iu ----*-** I/;;,::/' R ?.... ;;.Q'a:w \ ?;,";/' i-l/A R Comments:
Examined at areas of ID indic ation s ... l ----*----------*** ---------------------
------------------<
,__R_e s_u l_t s_: _N_RI_ .. _D_R_1D_E_ .. v_a1_18J ____________ ................................
...............
...... -.................................... _. ________ ...................................
... __ .. __ Percent of Coverage Obtained >90%: N/A Examiner 1 l N I A N I A Signature Reviewed Previous Date: N I A D ate Reviewer l.( 19,)11 Signatt1re Ji} D ate D ate Dat e 'l Other Level ................................................
Serial No. 17-187 Docket No. 50-336 Attachment 2, Page 6 of 12 Serial No. 17-187 Docket No. 50-336 Attachment 2, Page 7 of 12 J Serial No. 17-187 Docket No. 50-336 Attachment 2 , Page 8 of 12 West Side Plug a Attachment 1 Pre ss ure Te s t Parameter Worksheet (Sheet 6 o f 6) Serial No. 17-1 87 Docket No. 50-3 36 A tt achment 2 , Page 9 o f 12 Type of 1 es t: N ormal F lu id: S t e p Param e t e r s 1.3 In spec ti on R equire s V T-2 qualifie d exami n e r? .(circle one) YES NO 1.4 D esign p ressure 1.5 Hydrostatic Test P ress ur e (HTP) 1.6 P ressure ga u ge range limits; OD 1.7 1.8 Tust Me di u m an d Source 1.9 1.9.3 1.10 1.11.a 1.11.b 1.12 *---+* -* .. , .... 1.14 Test ho l d time (Ins ul a t e d 4 ho ur s, Non-in s ul ated 10 m in utes, o r other) V e.rt i cal d istance be tween l owest p ortion of hy d ros t atic t es t boundary an d test p ressu r e ga u ge (n egative if gauge is higher than lowest point; positive if ga u ge is l ower than lowe s t poin t) (ti. L i) = Vertical d i stance between hig h es t por t ion of hy d rostat i c test boundary and test pressure gauge (negative if gauge is h i gher than highest point; positive if gauge is l ower t h an highest poi nt) (ti. Lz) = Max P r ess ur e lim i t= 1.0 6 x HT P + (t. L i x 0.4335) = J.. l...&&deg; or Des i gn d oc um ent Min Press ur e limit= H T P + (ti. Lz x 0.4335) = J 'b1 , 5 or Design document If Min P r essure is greater than M ax Pr essure, /J. / 11 Min Press u re = 0.94 x Max Press ur e I n V ertica l d i s t a n ce, r e li ef va l ve to l owes t po int i n test bo und ary t. L:> = (n ega t ive if relief valve i s above l ow poin t of test b ow1dary; positive i f relief va l ve is below low p oint of te s t boundary)
Re lief valve setting= 1.06 x HT P + (t. L 3 x 0.4335) = or D esign d ocume n t Gagging device o r modi fication wit hin test bound aries. Se p arate W O's 0 (feet) O (feet) 0 (feet) NJ I ll Workshee t Pr e p ared By: D a t e: Leve l of U se R efe rence STOP. ;. THIN K * .. A C T REVIE W CM P 727 R ev. 001-00 23 of 3 1 
' Attachment 2 Hydrostatic Test Data Sheet (Sheet 1 of 1) SECTION A: Responsible Engineer to Complete D AS ME-XI SHOP T EST NON-AS ME-X I SHOP TE S T IXJ C OMPO N ENT Test Medium: fl Test pressures:
.......
Medium source: Min: ( J g 7 1 S I' Serial No. 17-187 Docket No. 50-336 Attachment 2, Page 10 of 12 f' 'I D NoN-ASME-Xi I N-PlANT T EST D P IPING Max: ( .(.l$ Te st pressure nominal: Pressure gauge calculated range: Te st hold t i me: Min: ( 3 3 7 1 5 . ) M ax: ( 9 (j 0 R elief va lve lo cation: Relief valve setting: f1iJA SECTION B: Examiner to Complete (VT-2 certified if " YES" in 1.3 , Attachment
: 1) Examiner signature:
PART C: *Responsible Engineer to Complete Dispo sitio n: T Name (p rint): 1 Signature:
PART D: ANll Review (if ASME piping or component)
Nam e (p rint): Signature:
Level of Use Reference
: f. v "<;; Level: "][ D ate: &#xa5;, J. o 17 0 Date: D ate: CMP727 Rev. 001-00 24 of 31 1; Serial No. 17-187 Docket No. 50-336 Attachment 2 , Page 11 of 12 04 20 2017 Serial No. 17-187 Docket No. 50-336 Attachment 2 , Page 12 of 12 04 20 2017 --t--}}

Latest revision as of 17:36, 4 February 2020

ASME Section XI Relief Request RR-04-26
ML17123A043
Person / Time
Site: Millstone Dominion icon.png
Issue date: 04/28/2017
From: Mark D. Sartain
Dominion, Dominion Nuclear Connecticut
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
17-187, RR-04-26
Download: ML17123A043 (29)
v • d • e


Text

~~

Dominion Nuclear Connecticut, Inc.

5000 Dominion Boulevard, G len All en, VA 23060 Web Address: www.dom.com U.S. Nuclear Regulatory Commission April 28 , 2017

' Dominion Serial No.17-187 Attention : Document Control Desk NRANJDC RO Washington, DC 20555 Docket No. 50-336 License No. DPR-65 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 2 ASME SECTION XI RELIEF REQUEST RR-04-26 Pursuant to 10 CFR 50.55a(z)(2) , Dominion Nuclear Connecticut, Inc. (DNC) requests relief from IWB-3142 of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code for the Millstone Power Station Unit 2 (MPS2)

'B' boric acid pump which has a through-wall leak in the stuffing box cover. The 'B' boric acid pump is one of two redundant pumps used for boron injection into the reactor coolant system via the suction of the charging pump .

Based on recent liquid penetrant examinations , hydrostatic testing, and comparison with typical ASME code design rules , DNC has assessed the condition of the stuffing box cover as structurally acceptable for continued service. Delivery of a new stuffing box cover is not expected until mid-June 2017 . Continued availability of the 'B' boric acid pump is needed to provide defense-in-depth for reactivity control until a permanent code repair of the stuffing box cover is complete .

Since ASME Section XI requires the defect be corrected prior to returning the affected component to service , compliance with the requirements of 10 CFR 50 .55a would resu lt in a hardship without a compensating increase in the level of quality and safety. to this letter describes the engineering evaluation of the defect, actions that will be implemented by DNC , and the basis for the proposed relief request. provides the non-destructive examination and hydrostatic test reports.

DNC requests approval of this relief request by May 5, 2017 to support Cycle 25 operation . This relief request has been approved by the Millstone Facility Safety Review Committee.

If you have any questions regarding this submittal , please contact Wanda Craft at (804) 273-4687.

Mark D. Sartain Vice President - Nuclear Engineering and Fleet Support

Serial No.17-187 Docket No. 50-336 Page 2 of 2

Attachment:

1. ASME Section XI Relief Request RR-04-26, Boric Acid Pump P-19B Stuffing Box Cover
2. Non-destructive Examination (NOE) and Hydrostatic Test Reports Commitments made in this letter: None cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd Suite 100 King of Prussia, PA 19406-2713 Richard V. Guzman Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 C 2 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No.17-187 Docket No. 50-336 ATTACHMENT 1 ASME SECTION XI RELIEF REQUEST RR-04-26 BORIC ACID PUMP P-19B STUFFING BOX COVER MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 1 of 13 Proposed Relief Request RR-04-26 In Accordance with 10 CFR 50.55a(z)(2)

--Hardship or Unusual Difficulty Without Compensating Increase in Level of Quality or Safety--

1. ASME Code Components Affected ASME Code Class: Code Class 2

Reference:

ASME Section XI , IWC-2500 Examination Category: Table IWC-2500-1 , Category C-H Item Number: C7.10

Description:

Millstone Power Station Unit 2 (MPS2) 'B' boric acid pump.

Components: The 'B' boric acid pump stuffing box cover is a casting of type 316 austenitic stainless steel per American Society fo r Testing and Materials (ASTM) A351 CF-8M.

2. Applicable Code Edition and Addenda

MPS2 is currently in the fourth 10-year inservice inspection (ISi) interval, which started on April 1, 2010 , and ends on March 31 , 2020. The ASME Section XI , 2004 Edition (No Addenda) applies to the ISi program .

3. Applicable Code Requirement

The ASME Code requirements for this relief request are those associated with Section XI , 2004 Edition , No Addenda, (Reference 8.1) and contained in Article IWB-3142, Acceptance.

4. Background

The 'B' boric acid pump is one of two redundant pumps used for boron injection into the reactor coolant system. The function of the boric acid pumps is for reactivity control , but the pumps are not credited in the Final Safety Analysis Report, Chapter 14 accident analyses. The design and normal operating parameters for the 'B' boric acid pump are provided below.

Design pressure = 150 psig Design temperature= 250 degrees Fahrenheit Operating discharge pressure = 112 psig Operating suction pressure = 4.5 psig Operating temperature= ambient temperature (110 degrees Fahrenheit)

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 2 of 13 Although MPS2 was designed and licensed to the GDC as issued on July 11 , 1967, DNC has attempted to comply with the intent of the newer General Design criteria to the extent possible, recognizing previous design commitments. MPS2 meets the intent of GDC 26, Reactivity Control System Redundancy and Capability, by employing two independent systems for controlling reactivity changes, including boric acid shim control, of which the boric acid pumps are a part. These systems compensate for long term reactivity changes such as those associated with fuel burnup , variation in the xenon and samarium concentrations, and plant cooldown and heatup. The 'B' boric acid pump provides a redundant means of delivering boric acid to the suction of the charging pumps to control reactivity during normal power operation and for such events as a Technical Specifications required cooldown to cold shutdown.

On February 28 , 2017, during a visual (VT-2) examination of the 'B' boric acid system, dry boric acid residue was identified on the pump stuffing box cover. The source of the boric acid could not be identified. This condition was entered into the corrective action program. During the following sh ift, the boric acid residue was cleaned and the pump was run for two hours in an attempt to determine the leak location and leak rate. No evidence of leakage was observed by the plant equipment operator who was stationed at the pump during the two-hour run.

On March 1, 2017, a follow-up ISi walkdown was performed and dry boric acid residue was found at the same location, but in a smaller quantity. The pump was declared non-functional and corrective action was initiated to identify the source of the leak.

On March 2, 2017, the 'B' boric acid pump was tagged out, but not drained, to support an informational liquid penetrant (LP) examination . The examination found no relevant or recordable indications. Following the LP examination , the 'B' boric acid pump was cleaned and then run for an additional time. After 10 minutes, a small accumulation of boric acid residue appeared as a wet, translucent spot. After 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of run time, the wet spot had increased in size to about 1/8 inch in diameter. Although a measurable leak rate could not be determined, growth of the wet spot confirmed the presence of a through -wall leak. The pump was subsequently isolated on March 9, 2017.

Because of limited access and complex surface geometry, direct volumetric examination of the leakage location from the outside surface of the assembled pump was not possible. However, based on an informational LP examination and visual examination of leakage during an extended pump run , DNC concluded the boundary leakage was likely the result of small voids or porosity present in the original stainless steel casting material.

DNC researched the original purchase order for the pump to identify initial testing associated with the boric acid pump. The pump was constructed in accordance with the draft ASME Code for Pumps and Valves for Nuclear Power, dated November

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 3 of 13 1968, as Class 2, and Combustion Engineering specification 18767-PE-404, Revision 1, dated February 9, 1972. The Combustion Engineering specification refers to the ASME code for testing requirements. Section B of the draft ASME code contains the requirements for Class 2 pumps and valves. Article 23, sub-article 2314 specifies special requirements related to Class 2 components. Normally, this sub-article would require that radiography be performed for a cast product.

However, sub-article 2314 identifies that the special requirements do not apply to materials for pumps and valves with inlet piping connections of four inches and less in nominal pipe size unless otherwise noted in the design specification. The inlet piping to the boric acid pump is less than four inches and the design specification did not invoke a radiography requirement for this pump. Initial testing did include an LP examination and a hydrostatic test and the examination and test had satisfactory results.

Following discovery of the through-wall leak, DNC submitted a purchase order to the pump vendor for a new stuffing box cover. Due to the long lead time to fabricate a replacement stuffing box cover, a code repair of the 'B' boric acid pump was not possible prior to the scheduled shutdown date for 2R24. However, based on engineering assessment of the as-found condition, DNC had high confidence that structural integrity of the stuffing box cover would be maintained for the duration of Cycle 24 operation and execution of the plant shutdown and core offload for 2R24.

Therefore, on March 29 , 2017, DNC requested relief (Reference 9.1) from IWB-3142 of Section XI of the Code to provide continued availability of the 'B' boric acid pump for the remainder of Cycle 24 operation and execution of the plant shutdown and core offload for 2R24. Compliance with the requirements of 10 CFR 50 .55a would have resulted in a hardship without a compensating increase in the level of quality or safety. Verbal approval of the relief request was granted by the NRC the same day (ADAMS Accession No. ML17088A719).

The stuffing box cover on the 'B' boric acid pump has since been removed for furthe r characterization of the through-wall flaw. Based on LP examination and hydrostatic testing , DNC has assessed the stuffing box cover as structurally acceptable for continued service. Details of that evaluation are provided in Section 6 below.

5. Reason for Request

The 2004 ASME Section XI code was reviewed for acceptance standards associated with the stuffing box cover leak. Table IWC-3410-1 , Acceptance Standards, indicates for pressure retaining components (examination category C-H),

the acceptance standard is IWC-3516. IWC-3516 refers to IWB-3522. IWB-3522 refers to IWB-3142 for corrective actions.

Article IWB-3142, Acceptance, specifies that a component with a relevant condition is unacceptable for continued service unless the requirements of IWB-3142.2, 3 or 4 have been satisfied. All three options have been considered. IWB-3142.2 is related to acceptance by performing supplemental examinations. This section is about

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 4 of 13 sizing of defects for comparison to ASME criteria to allow leaving a flaw in service.

This option is not applicable to a through-wall condition. IWB-3142.4 is related to determining acceptance by analytical evaluation. This option is not possible because there is not a code-specified methodology for analyzing the condition . Of the three options available for acceptance of a relevant cond ition , a repair/replacement per IWB-3142.3 is the only viable option for addressing the current observed condition.

Although MPS2 can operate without boric acid pumps, maintaining the 'B' boric acid pump available provides additional assurance that the boric acid injection function will remain available for reactivity changes, if needed, until a permanent code repair of the stuffing box cover can be performed . Since delivery of the replacement stuffing box cover is not expected until mid-June, 2017, compliance with the requirements of 10 CFR 50.55a would result in a hardship without a compensating increase in the level of quality or safety.

6. Proposed Alternative and Basis for Use 6.1 Proposed Alternative DNC has assessed the condition of the stuffing box cover as structurally acceptable for continued service. Therefore, in lieu of code repair prior to startup, DNC proposes to keep the pump in service with the identified indications until a replacement part is delivered and a permanent code repair can be performed.

DNC will inspect the affected pump stuffing box cover each shift for leakage until the pump is removed from service for repair. The inspection results will be documented. Should leakage increase, an engineering evaluation will be performed to reassess structural integrity and the impact of the leakage on nearby equipment. If structural integrity cannot be maintained, the pump will be isolated.

6.2 Basis for Use During 2R24, the 'B' boric acid pump was disassembled to further evaluate the structural integrity of the stuffing box cover (Figure 1). The NOE and hydrostatic test reports are provided in Attachment 2.

Liquid penetrant (LP) examinations were performed on both the inside and outside surfaces of the stuffing box cover. LP examination of the outside surface identified two rounded indications, approximately 1/16 of an inch apart, in the area of the observed leak (Figure 2). LP examination of the inside surface identified three rounded indications; two indications were located near one leak off port (in the area of the observed leakage) (Figure 3) , while the third

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 5 of 13 indication was offset approximately 180 degrees near the opposite leak off port.

No recordable indications were identified on the outside of the cover in this area. Table 1 provides the location and size of the indications.

Table 1: B' Boric Acid Pump Stuffing Box Cover LP Indications Indication Location Diameter of bleedout (inches) 1 Outside Surface - East Side 1/32 2 Outside Surface - East Side 1/32 3 Inside Surface - East Side 3/32 4 Inside Surface - East Side 3/16 5 Inside Surface - West Side 3/16 DNC attempted to perform volumetric examination of the stuffing box cover using ultrasonic testing (UT). Although the smallest available transducer was used, the UT did not produce any useful information because the UT transducer was not able to maintain suitable surface contact. DNC considered performing radiography. However, due to the dimensions and geometry of the stuffing box cover, DNC determined that examination of the leakage area using radiography was not practical.

DNC performed an informational hydrostatic test of the stuffing box cover. The hydrostatic test was performed at a pressure of 220 psig and held for 10 minutes. Although the test did not result in any measurable leakage, indication of leakage (slight wetting) at two locations was visible through the use of an LP developer. The first location was in the area where the leakage was first observed and the second location was on the opposite side of the cover approximately 180 degrees from the first location. The location where slight wetting was observed on the outside of the stuffing box cover corresponds to the location of the identified indications.

Based on the results of the above inspections, the stuffing box cover pressure boundary leakage is likely due to small casting void defects or porosity that enable a through-wall pathway for leakage. The NOE results (very small rounded indications), the very low leakage at hydrostatic conditions, and the propensity of stainless steel castings to have small amounts of porosity, lead DNC to conclude that porosity is the most likely explanation for what is observed. Alternative explanations have been considered, but determined to be unlikely, as discussed below.

Structural Evaluation Leak Location and Operating Conditions - The location of the leakage is on the portion of the stuffing box cover that surrounds the pump shaft. At this

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 6 of 13 location, the stuffing box seal cover pressure cannot be measured but a typical rule for estimating stuffing box pressures is:

P = (Poutlet - Pinlet) / 4 + Pini et P =stuffing box pressure, psig Poutlet =pump design discharge pressure, psig = 150 psig Pinlet =pump suction pressure, psig = 4.5 psig The pump design discharge pressure is 150 psig and the suction pressure is 4.5 psig. These values give an estimate for the stuffing box pressure of 41 psig using the above rule. For conservatism, 50 psig is assumed.

Material Performance and Degradation Potential - The figure at right shows the configuration of the boric acid pump. The boric acid pump has been in service since initial plant operation. The cross-hatched area on the left is the stuffing box cover casting, and the impeller is the cross-hatched component on the right. The stuffing box cover is made from cast type 316 austenitic stainless steel per specification ASTM A351 CF-BM, as shown on the vendor drawing.

Type 316 stainless steel has excellent general corrosion resistance to the boric acid solution that is the process fluid for this pump. Based on testing done for Electric Power Research Institute (Reference 9.2), the general corrosion 11 rate in the process fluid is too small to measure.

The other internal parts of the pump are made from cast or wrought type 316 stainless steel.

Type 316 stainless steel, either cast or wrought, is not susceptible to pitting or stress corrosion cracking in this environment. The cast version of 316 stainless steel is not susceptible to thermal aging at the low temperature at which this pump operates. Additionally, mechanical loads due to normal operation, including pump vibration, are low and would not be anticipated to result in service induced flaw growth. With these considerations, it is concluded that there are no active aging degradation mechanisms for this component that would cause initiation and through-wall growth of a planar flaw. The remaining reasonable explanation for the leakage is that there is a leakage pathway via small voids, or porosity, originally present in the cast material. Similar instances of this phenomenon have been documented by other licensees (References 9.3 and 9.4). As discussed below,

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 7 of 13 such small imperfections do not significantly affect the structural integrity of the component.

The absence of an active degradation mechanism also supports the conclusion that the currently observed leak rate will remain nearly constant for the duration of this requested relief.

Structural Integrity - There is no code-specified methodology for evaluating the structural integrity of this type of component when through-wall leakage is detected. However, the stuffing box cover in the area of concern can be conservatively bounded as a cylindrical section, similar to a cylindrical vessel with localized leakage. The Code of Construction for the pump is the draft ASME Code for Pumps and Valves for Nuclear Plants, 1968. The stuffing box cover material is ASTM A351 CF-BM which has an allowable design stress of 17.5 ksi. The inside diameter of this section is approximately 2.5 inches.

Considered as equivalent to a cylindrical vessel, the minimum wall thickness would be calculated per ASME Ill NC-3324 as:

tmin = p RI (S - 0.6 P)

The values for the parameters in this formula are:

P =stuffing box pressure, psig = 50 psig R = radius of the stuffing box = 2.5/2 = 1.25 inches S =stuffing box allowable stress= 0.8 x 17.5 = 14 ksi (including a casting quality factor of 0.8)

The result is tmin = 0.0045 inch.

The actual wall thickness of this section in the area of the observed leakage is not specified on drawings but is estimated to be approximately 0.250 inch based on the minimum wall thickness required for valves by the construction code. The evaluation result of 0.0045 inch required wall thickness, in comparison to the approximately 0.250 inch estimated actual wall thickness (Figure 4), results in a factor of about 56. This demonstrates that this portion of the pump stuffing box cover is not challenged by the pump stuffing box pressure. Additionally, this portion of the stuffing box cover is not required to withstand any significant mechanical loading. This portion of the casting supports only the mechanical shaft seal. The pump shaft is supported independently of the stuffing box cover and seismic loading from the shaft, impeller, and piping nozzles are transferred through the pump frame adaptor and pump casing to anchorage feet attached to the pump casing. The loads do not pass through this portion of the stuffing box cover. Thus the minimum wall thickness calculation reasonably demonstrates the structural integrity of the pump stuffing box cover in the area of the observed leakage.

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 8 of 13 Functionality - The above structural integrity evaluation supports the conclusion that the pump is capable of performing its intended function of transferring concentrated boric acid from the boric acid storage tank to the suction of the charging pumps and will retain this capability for the duration of the requested relief. The overall mechanical integrity of the pump will be maintained such that the pump will be able to generate sufficient head for the required flow, and since the pressure boundary is maintained, there would be no significant diversion of boric acid intended for injection into the charging pump suction.

Conclusion ASME Section XI requires the defect be corrected prior to returning the affected component to service. However, compliance with the requirements of 10 CFR 50.55a would result in a hardship without a compensating increase in the level of quality and safety pursuant to 10 CFR 50.55a(z)(2) . The structural integrity of the stuffing box cover cannot be demonstrated in accordance with a code-specified methodology. However, based on LP examination , hydrostatic testing and comparison with typical ASME code design rules, it is concluded that there is reasonable assurance that the structural integrity and functional requirements of the pump will be maintained during the requested period of relief. Delivery of a new stuffing box cover is not expected until mid-June 2017. Therefore, the continued availability of the 'B' boric acid pump is needed to provide defense-in-depth for reactivity control until a permanent code repair of the stuffing box cover can be performed.

7. Duration of Proposed Alternative This relief is requested to be effective upon approval and until a permanent code repair of the boric acid pump stuffing box cover can be performed during Cycle 25.

Delivery of the stuffing box cover is expected in mid-June. A permanent code repair will be performed as soon as practical after receipt of the part, but no later than startup from the next refueling outage.

8. Precedent Email from R. Guzman to W. Craft - Millstone Power Station Unit 2, Verbal Authorization by the NRR staff - Relief Request No. RR-04-25 (CAC No. MF9497) ,

dated March 29 , 2017 (ADAMS Accession No. ML17088A719).

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 9 of 13

9. References 9.1 Dominion Nuclear Connecticut Inc., Millstone Power Station Unit 2, ASME Section XI Relief Request RR-04-25 , dated March 29, 2017 (ADAMS Accession No. ML17090A110).

9.2 2012 EPRI Technical Report: Materials Reliability Program: Boric Acid Corrosion Guidebook, Revision 2: Managing Boric Acid Corrosion Issues at PWR Power Stations (MRP-058, Rev 2).

9.3 NRG letter from J. Quichocho (USNRC) to W. Gideon (CP&L), dated December 12, 2012, "H. B. Robinson Steam Electric Plant, Unit No. 2 - Relief Request-07 from Immediate ASME Code Repair of Refueling Water Storage Tank Drain Valve (Safety lnjection-837) for Fifth10-year lnservice Inspection Program Plan (TAC NO. ME9747)." [ADAMS Accession Number ML12325A612]

9.4 NRG Letter from J. B. Martin (USNRC) to C. A. Schrock (WPSC) dated November 5, 1993, related to Notice of Enforcement Discretion associated with Residual Heat Removal Pump Casting Void . (As identified in WPSC letter from C. A. Shrock to USNRC, dated December 6, 1993, "Reportable Occurrence 93-019-00").

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 10 of 13 Figure 1

'B' Boric Acid Pump Stuffing Box Cover

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 11 of 13 Figure 2 Rounded Indications on Outside Surface of Stuffing Box Cover (In area where leakage was observed)

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 12 of 13 Figure 3 Rounded Indications on Inside Surface of Stuffing Box Cover

Serial No.17-187 Docket No. 50-336 Attachment 1, Page 13 of 13 Figure 4 Photo Showing Wall Thickness of Stuffing Box Cover

Serial No.17-187 Docket No. 50-336 ATTACHMENT 2 NON-DESTRUCTIVE EXAMINATION AND HYDROSTATIC TEST REPORTS MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.

Serial No.17-187 Docket No. 50-336 Attachment 2, Page 1 of 12 Liquid Penetrant Examination (Page 1 of l)

-******* * -- *~ - ---*--

Site/Unit: Millstone Procedure: ER-AA-NDE-PT-301 Outage No.: 2R24 Summary No.: NI.A Pi-ocedure Rev.: 7 .Repott No.: NIA Workscope: .E11g Information Work Order No.; 53103060177 Page: I of <{*

Code: N/A CatJJtem: NIA Location: -5' Aux Bdg Drawing No.: 25203-29163 SH 5

Description:

Pl9B Stuffing Box Cover ID Exam System JD: M2Pl9B Component JD: Pl 9B Stuffing Box Cover

..... --*********** I"'U!"""~* 0 Size/Length: 0 NJ.A.

NIA Limitations: NI A Light Meter Mfg.: Spectroline Serial No.: MTE-02951 Illumination: > 100 fc Temp. Tool Mfg.: KTA Tator  ! Serial No. :.M"11i=o~8 Surface Temp.: 72.5 op Comparator Block Temp.: Side ANIA °F SideB NIA °F

.. .. ..........i...

IReso lution; Nl~**-*** *-

ISurface Condition: Machined f---

Lo/Wo Location: C/L of1hreaded plug I Top edge of Cover

~--- - ---* ~--------~----------~--------,

Cleaner Penetrant .Remover Developer 1 Brand Magnaflux Magnat:hrx Magnaflux Magnatlux

                                              • --****-1-- - -- - - - -- - t - - - - -* - ---l Type SKC-S SKL-SP2 SKC-S SKD-S2 Batch No. 15El5K 13JIOK 12G04K 13G07K

- -*******-**-----+--- - -- - - - + -

Time Evap. 4min Dwell 15min Evap. I min . Develop 10 min

!----~- *-*-- **** -------'---------***- * **-+----------~-----*

Time Exam Started: 09:27 Time Exam Completed: 10:10 Indication Loe Loe Diameter Length Type Remarks 1_ _N ~'= o ~.--+---"L"---+---" w.__+--****- - - --+-"""Ri""'IJ"'" , -+- - -- - * - - - -*

. !['J2C<..l . -;i\fy," 3 ;):.) ...lfl\

'.2... '.}-Bo-> ~"'!~' .?:D~' -~--+----+- t-.l/A ~--.....t:;~ $ \ J.<. t'\~o..k :t:D o(' co'\Je.Jr

_".:> l/~ ew ?..'/?i

0

....if A 3..N~t "'1e.::;," ~id.<- ...i O>\* :t::t>.. .Qf_c~O\J~e~((

~-------<

Comments: Examined machined JD of stuifmg box cover Results: NR! 0 RI 0 Eval ~

Percent of Coverage Obtained >90%: NIA R.evicwed Previous Date: NIA Examiner Level Siguatuni Date Reviewer Date II Lj l'l 11 Examiner Level 'S gnatw* Dale NIA Other Level Signature Date Sig11ature Date NIA

Serial No.17-187 Docket No. 50-336 , Page 2 of 12

Serial No.17-187 Docket No. 50-336 , Page 3 of 12

Serial No.17-187 Docket No. 50-336 , Page 4 of 12

Serial No.17-187 Docket No. 50-336 Attachment 2 , Page 5 of 12 Liquid Penetrant Examination (J'agc I of I )

Site/Unit: Millstone Procedure: ER-AA-NDE-PT-30 1 Outage No.: 2R24 Summary No.: NJ.A Procedure Rev.: 7 Repo1tNo.: N/A

..........___.._..__.........._ ........._____--;,__--- -- -- - - - -- -t - - - - - - - - - ------1 Wo!'.kscope: Eng huorr.nntion Work Order No.: 53103060177 Page: I of L\

Code: N/A Cat/Item: NIA J~~3-~o_n_:_*:i_**_A_ux_*_B_d_g_ _ _ __ ___.

Drawing No.: 25203-29163 SH 5

Description:

Pl 9B Stuffing Box Cover OD Exam

      • ** ** ***** ****************** * ************* * **- * ------~--------------..------------*-*-

System JD: M2Pl9B Mat/111ickncss: 0 N JA

......................................- -- -- - - - - - - - - - + - -- -- - - - -- - - ---<

Component JD: Pl9B Sni.ffing Box Cover I Size/Length: 0 ..J/A.

>---------------------------*-* --* ---*-~----------------

Limitations: NIA 1

Light Meter Mfg.: Spectrolinc Serial No. : MTE-02951 l1Jumination; > 100 fc Temp. Tool Mfg.: KTA Tator l Serial No.: MTE-01887 Surface Temp.: 72.5 °F t---------------L----------~-----'------*----- --*****-**** * *-------<

Comparator Block Temp. : Side A NIA °F Side B NIA °F IResolution: NIA Lo/Wo Location: Cl1, of threaded plug i Top edge of Cover ISurface Condition: As cast with ground areas

    • --**-*** ---*-****---**- *1- - -- - - - -- -
  • Cleaner Penetraut Remover i Developer Brand
  • Magna11ux  ! Magnatlux I

[ Magnafiux I

Magnaflux Type SKC-S SKL-SP2 SKC-S SKD-S2 Batch No. 15El5K J3JJOK 12G04K 13G07K Tinle Evap. 3 min Dwcll 15 min Evap. J min Develop lO min Time b'xam. Started: 10:25 Time Exam Completed: 11:10 Indication Loe Loe Diameter Length Typt: Remarks No. L w R/L

- - - - * -** 3.l:PS!.iu ~f)J.~ I/;;,::/' ~IA R

?....  ;;.Q'a:w -;i'/~" \ ?;,";/' i-l/A R Comments: Examined at areas of ID indications

.. l

,__R_esu_l_ts_:_N_RI _.. _ D_R_1D_ E_..v_a1_18J _ _ _ __ _______ .....................................................- ...................................._.________......................................__..__ ~

Percent of Coverage Obtained >90%: N/A Reviewed Previous Date: NIA Date Reviewer Signatt1reJi} Date l .( 19,)11 1

Examiner Date l NIA

'l Other Level Signature Date NIA

.............................................. ..*--------------~-------------------~

Serial No.17-187 Docket No. 50-336 , Page 6 of 12

Serial No.17-187 Docket No. 50-336 , Page 7 of 12

Serial No.17-187 Docket No. 50-336 Attachment 2, Page 8 of 12 West Side Plug a J

Serial No.17-187 Docket No. 50-336 Attachment 2, Page 9 of 12 Attachment 1 Pressure Test Parameter Worksheet (Sheet 6 of 6)

Type of 1est: Normal F luid:

Step Parameter s 1.3 Inspection Requires VT-2 qualified examiner ? .(circle one) YES NO 1.4 D esign pressure 1.5 Hydrostatic Test P ressure (HTP) 1.6 Pressure gauge range limits; OD 1.7 1.8 Tust Medium and Source 1.9 1.9.3 Test hold time (Insulated 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, Non -insulated 10 m inutes, or other) 0 Ve.rtical distance between lowest p ortion of hydros tatic test boundary and test pressure gauge (negative if gauge is higher than lowest point; positive if gauge is lower than lowest point) (ti. Li) = (feet) O 1.10 Vertical distance between highest portion of hydrostatic test boundary and test pressure gauge (negative if gauge is higher than highest point; positive if gauge is lower than highest point) (ti. Lz) = (feet) 0 1.11.a Max Pressure limit = 1.06 x HTP + (t. Li x 0.4335) = J.. l...&° or Design document Min Pressure limit= H TP + (ti. Lz x 0.4335) = J 'b1 , 5 or Design document 1.11.b If Min Pressure is greater than M ax Pressure, /J./

Min Pressure = 0.94 x Max Pressure I n11 Vertical distance, relief valve to lowest point in test boundary (nega tive if relief valve is above low point of test bow1dary;

t. L:> = (feet) NJ 1.12 positive if relief valve is below low point of test boundary) Ill Relief valve setting= 1.06 x HTP + (t. L3 x 0.4335) =
  • ---+* -* . ,.. or D esign documen t Reiiei'-;a1~e *g;;ggfug Ci~;;r~;c;~*mo<lifi~~tioii ~eq uired. ~~--~

1.14 Gagging device or modification within test boundaries.

Separate WO 's Worksheet Prep ared By: D ate :

Level of Use  ;.

CMP 727 Reference * ..

STOP . THINK ACT REVIEW Rev. 001 -00 23 of 31

Serial No.17-187 Docket No. 50-336 Attachment 2, Page 10 of 12 I' f' 'I Attachment 2 Hydrostatic Test Data Sheet (Sheet 1 of 1)

SECTION A: Responsible Engineer to Complete D AS ME-XI SHOP TEST ~ NON-AS ME- XI SHOP TEST D NoN- ASME-Xi IN-PlANT TEST IXJ COMPONENT D PIPING Test Medium: fl Test pressures:

1--~~~~~-.J. .......~..t.K...;'-'l......,_~~~~--1 Medium source: Min: ( Jg 71 S Max: ( .(.l$

Test pressure nominal: Pressure gauge calculated range:

Test hold time: Min: ( 3 3 71 5 . ) Max: ( 9(j 0 Relief valve location: Relief valve setting: f1iJA SECTION B: Examiner to Complete (VT-2 certified if "YES" in 1.3, Attachment 1) 1; Level: "][

Examiner signature: Date: ¥, J. o 17 PART C: *Responsible Engineer to Complete Disposition:

T 0 Name (print):

1 Signature: Date:

PART D: ANll Review (if ASME piping or component)

Name (print) :

Signature: Date:

f.

Level of Use CMP727 Reference ~.sf~w; Rev. 001-00 t>~--~~.~ ~,

v "<;;

24 of 31

Serial No.17-187 Docket No. 50-336 , Page 11 of 12 04 20 2017 ~

Serial No.17-187 Docket No. 50-336 , Page 12 of 12 04 20 2017 ~

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